In modern aircraft, the primary flight display screens now include a three-dimensional synthetic representation of the outside world. These representations may comprise an indicator of the flight plan followed by the aircraft. Older representations are of the “highway in the sky” type. The trajectory to be followed is then shown to the pilot in the form of a three-dimensional path superposed on the synthetic landscape. The width of the path is representative of the positioning tolerances of the aircraft in a horizontal plane. These tolerances are covered by aeronautical standards.
One of the drawbacks of these representations is that the represented path does not comprise clear indicators of angular deviations, both lateral and vertical, between the actual position of the aircraft and the path to be followed. As a result, the pilot lacks precise information in order to correct the trajectory of the aircraft.